Realstrukturuntersuchungen von hydrothermal auf kleinen Rhomboederflächen gewachsenen Quarzeinkristallen

Crystals of α-quartz, which were grown from seeds of the minor rhombohedral face (1 011) and the basal face (0001), were examined with optical, etching and x-ray topographic methods. In agreement with the literature we have observed that there is a heavier coloration due to Al-impurity after x-ray irradiation, in the (1 011)-growth direction, than in others; the basal growth sector remains colourless. The strong coloration must not be in agreement with a high dislocation density. The dislocations in the rhombohedral growth are characteristically different from that of the basal growth. Correlation of the observed surface structure, as hillocks, terraces, and spirals with the distribution of etch pits is not observable.